{"id":20755222,"url":"https://github.com/formix/retroz","last_synced_at":"2026-03-13T10:32:50.092Z","repository":{"id":84235153,"uuid":"149890019","full_name":"formix/RetroZ","owner":"formix","description":"An S80 Single Board Retro Computer","archived":false,"fork":false,"pushed_at":"2020-03-30T11:36:27.000Z","size":3784,"stargazers_count":20,"open_issues_count":0,"forks_count":4,"subscribers_count":2,"default_branch":"master","last_synced_at":"2025-12-19T20:24:09.947Z","etag":null,"topics":["board","bom","electronics","pcb-layout","retrocomputing","sio","z80"],"latest_commit_sha":null,"homepage":"","language":"VBA","has_issues":true,"has_wiki":null,"has_pages":null,"mirror_url":null,"source_name":null,"license":"apache-2.0","status":null,"scm":"git","pull_requests_enabled":true,"icon_url":"https://github.com/formix.png","metadata":{"files":{"readme":"README.md","changelog":null,"contributing":null,"funding":null,"license":"LICENSE","code_of_conduct":null,"threat_model":null,"audit":null,"citation":null,"codeowners":null,"security":null,"support":null,"governance":null,"roadmap":null,"authors":null,"dei":null,"publiccode":null,"codemeta":null}},"created_at":"2018-09-22T15:32:54.000Z","updated_at":"2025-09-29T21:56:18.000Z","dependencies_parsed_at":"2023-05-24T02:15:27.071Z","dependency_job_id":null,"html_url":"https://github.com/formix/RetroZ","commit_stats":null,"previous_names":[],"tags_count":2,"template":false,"template_full_name":null,"purl":"pkg:github/formix/RetroZ","repository_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/formix%2FRetroZ","tags_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/formix%2FRetroZ/tags","releases_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/formix%2FRetroZ/releases","manifests_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/formix%2FRetroZ/manifests","owner_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners/formix","download_url":"https://codeload.github.com/formix/RetroZ/tar.gz/refs/heads/master","sbom_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/formix%2FRetroZ/sbom","scorecard":null,"host":{"name":"GitHub","url":"https://github.com","kind":"github","repositories_count":286080680,"owners_count":30465427,"icon_url":"https://github.com/github.png","version":null,"created_at":"2022-05-30T11:31:42.601Z","updated_at":"2026-03-13T06:34:02.089Z","status":"ssl_error","status_checked_at":"2026-03-13T06:33:49.182Z","response_time":60,"last_error":"SSL_connect returned=1 errno=0 peeraddr=140.82.121.5:443 state=error: unexpected eof while reading","robots_txt_status":"success","robots_txt_updated_at":"2025-07-24T06:49:26.215Z","robots_txt_url":"https://github.com/robots.txt","online":false,"can_crawl_api":true,"host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":["board","bom","electronics","pcb-layout","retrocomputing","sio","z80"],"created_at":"2024-11-17T09:23:55.328Z","updated_at":"2026-03-13T10:32:50.063Z","avatar_url":"https://github.com/formix.png","language":"VBA","funding_links":[],"categories":[],"sub_categories":[],"readme":"# RetroZ SBC S80\r\nA minimalist single board Z80 retro computer based on the S80 design \r\nspecifications.\r\n\r\nThis board is developped using the S80 physical specifications. The \r\nspecifications are not currently available online but I plan to fix that in a \r\nfuture revision.\r\n\r\n![RetroZ SBC for S80 Architecture](https://raw.githubusercontent.com/formix/RetroZ/master/Documents/RetroZ-SBC-Front.png)\r\n*Front of the board*\r\n\r\n[Back of the board](https://raw.githubusercontent.com/formix/RetroZ/master/Documents/RetroZ-SBC-Back.png)\r\n\r\nYou can find the board schematic as a PDF [here](https://github.com/formix/RetroZ/blob/master/Documents/RetroZ-SBC.pdf).\r\n\r\n## BOM\r\n\r\nYou can download the BOM [here](https://github.com/formix/RetroZ/blob/master/Projects/RetroZ-SBC/RetroZ-SBC-BOM.ods?raw=true). It is an Open Document Worksheet file and you should be able to open it with Open/Libre Office or MS Excel. If you have issue, contact me.\r\n\r\n| Comp.                      | Mouser#  | Digikey#      | Mfr#               | Qty | Description                        | \r\n|----------------------------|----------|---------------|--------------------|-----|------------------------------------| \r\n| C1,C2                      |          |               | C317C200J5G5TA     | 2   | 20pf Capacitor                     | \r\n| C3,C4                      |          |               | FG28C0G1H470JNT06  | 2   | 47pF Capacitor                     | \r\n| C5,C6,C7,C8,C9,C10,C11,C12 |          |               | C322C104K5R5TA7301 | 8   | 0,1uF Capacitors                   | \r\n| D1                         |          |               | 151051VS04000      | 1   | Green Led 5mm                      | \r\n| D2,D3                      |          |               | 151031SS06000      | 2   | Red Led 3mm Round, FwdV 2.2        | \r\n| IC1                        |          |               | ADM803TAKSZ-REEL7  | 1   | Power-on Reset chip                | \r\n| IC2                        |          |               | AT28C256-15PU      | 1   | EEPROM 256kbit 28-Pin PDIP         | \r\n| IC2,IC3                    |          |               | 4828-6004-CP       | 2   | CONN IC DIP SOCKET 28POS TIN       | \r\n| IC3                        |          |               | AS6C62256-55PCN    | 1   | IC SRAM 256K PARALLEL 28DIP        | \r\n| J1                         | 485-2223 | 1528-1385-ND  | 2223               | 1   | Adafruit stacking header 2x20      | \r\n| J2,J3                      | 485-85   | 1528-1074-ND  | 85                 | 1   | STACKING HEADER ARDUINO SHIELD     | \r\n| J4                         |          |               | PRPC005DAAN-RC     | 1   | 5x2 Pin Connector                  | \r\n| J4,J6                      |          |               | QPC02SXGN-RC       | 2   | 1x2 Shunt connector                | \r\n| J5                         |          |               | 629105150521       | 1   | USB Microb B SMT Connector         | \r\n| J6                         |          |               | PRPC004DAAN-RC     | 1   | 4x2 Pin Connector                  | \r\n| R1                         |          |               | RNF14FTD1M00       | 1   | 1M Ohm Resistor                    | \r\n| R10,R11                    |          |               | RNF14FTD332R       | 2   | 332 Ohm resistor                   | \r\n| R2                         |          |               | RNF14FTD1K00       | 1   | 1k Ohm Resistor                    | \r\n| R3,R4,R5,R6,R12,R13,R14    |          |               | RNF14FTD10K0       | 7   | 10k Ohm Resistor                   | \r\n| R7                         |          |               | RNF14FTD221R       | 1   | 221 Ohm Resistor                   | \r\n| R8,R9                      |          |               | RNF14FTD27R4       | 2   | 27 Ohm Resistors                   | \r\n| SW2                        |          |               | BD01               | 1   | DIP Switch x1                      | \r\n| U1                         |          |               | 74LS32             | 1   | Quand OR                           | \r\n| U2                         |          |               | 74HCT04            | 1   | Hex Inverter Schmidt Trigger       | \r\n| U3                         |          |               | Z84C0008PEG        | 1   | Z80 CPU                            | \r\n| U3,U5                      |          |               | 4840-6004-CP       | 1   | 40 pin (2 x 20) DIP socket 15,24mm | \r\n| U4                         |          |               | SN74LS138N         | 1   | 3 to 8 Decoder/Demux               | \r\n| U5                         |          |               | Z84C4208PEG        | 1   | Z80 SIO/2                          | \r\n| U6                         |          |               | FT230XS-U          | 1   | UART to USB                        | \r\n| U7                         |          |               | 74LS92             | 1   | Dodecade counter (div. By 12)      | \r\n| Y1                         |          |               | ECS-73-20-5PX-TR   | 1   | 7,3728 MHz Crystal                 | \r\n \r\n\r\n## Development Note\r\n\r\n### 2019-01-15\r\nThe review phase is done! I just sent the board to production. I should get the\r\nfinished board next week.\r\n\r\n### 2019-01-26\r\nI recieved my boards (10 boards!) yesterday. I just finished creating the BOM \r\nand sorted through my parts to order what is missing. I expect to recieve my \r\norder in the coming week. I'll work on the NASCOM Basic once I got the \r\ncomputer assembled. Stay tuned!\r\n\r\n### 2019-08-03\r\nIt's been a while since I updated that README file but as you can see,\r\nI'm committing regularily on the project. Simply put, I'm too busy playing \r\nwith my working RetroZ SBC computer to update the front documentation. It is \r\ntime to fix that, continue reading to get the full update.\r\n\r\n## What's Inside?\r\nThe RetroZ-SBC computer is a 8MHz Z80 CPU clocked at 7.3728 MHz. It supports \r\nup to 32kB of ROM and 32kB of RAM. An SIO/2 chip is connected to the USB \r\nMicro B socket using an FTDI serial converter. Rx and Tx leds let you know \r\nwhen the computer communicates over USB. The whole computer is powered through\r\nthe same USB port and a power-on reset monitor resets the computer at startup.\r\nA Reset button allows warm computer restart. An On/Off DIP switch controls the\r\npower state of the computer and a power led indicator let you know that the \r\nbeast is powered. All the Z80 processor pins are available through the 40 pins\r\nstacking header plus some other on the User Port A. User Port B stacking\r\nheader is fully available (8 pins) for child boards future projects.\r\n\r\n## The Connection\r\nThe USB to serial conversion is made possible thanks to an FTDI chip \r\n[behind the board](https://raw.githubusercontent.com/formix/RetroZ/master/Documents/RetroZ-SBC-Back.png) \r\nand is clocked at 115200 bauds by default. This speed can be changed \r\nprogrammatically through the Z84C40 (Zilog SIO/2) registers. On a Windows\r\nmachine the device can be accessed using **COM5**. For a \r\nMac/Linux box it is **/dev/ttyUSB0**. Hardware flow control CTS/RTS is fully \r\nwired so feel free to flood the console with whatever you get, it should \r\nhandle it.\r\n\r\n## Technical Reference\r\n### Power and commnunication over USB\r\nUsing a single USB Micro-B wire, it is possible to power-up and communicate \r\nwith the computer. There is a DIP switch to set the computer on or off and a \r\npower indicator led indicates when the computer is powered on. There is also\r\na power line monitor chip (IC1) that pull the /RESET line LOW for 240 ms \r\nafter power on.\r\n\r\n### Serial Communication\r\nSerial communication is achieved using a Z84C42 SIO/2 chip. The serial port A \r\nis connected to the USB jack through an FTDI UART to USB 2.0 converter. Rx \r\nand Tx leds indicate when communication occurs on that port. The serial port \r\nB is connected back into the User Port A (J2) PIN 2 (RxB) and Pin 3 (TxB) for \r\nslave cards serial communications.\r\n\r\n**The serial port A clock** is directly tied to the clock and can be changed \r\nprogrammatically from the SIO/2 registers. In the NASCOM Basic provided, it is \r\nset to 115200 by default.\r\n\r\n**The serial port B clock** The default speed is set to 115200 bauds as well. \r\nAgain, that speed can be programmatically changed. The serial clock on port B \r\ngoes through a dodecade counter and can be further adjusted using the \r\n`Clock div.` (J6) jumper that offers another set of 1,2,6 and 12 dividers. \r\nThat gives a wide variety of standard baud rates down to 9600 bauds.\r\n\r\n### Onboard memory control\r\nThe PIN 1 of the User Port A is pulled low with a 2k resistor. This is the \r\non-board memory enable input pin (/ME). To disable onboard memory, an \r\nexpansion card can set that pin HIGH. This would be the case with a memory \r\nexpansion board. It can be hardwired to 5V to disable the onboard memory \r\ncompletely or it can be tied to some logic to leverage the on-board memory as \r\nneeded.\r\n\r\n### Interrupt Chaining\r\nThe RetroZ SBC design allows chaining interrupts of up to 4 slave boards. The\r\nonboard SIO/2 IEO pin is hardwired to the User Port A INT0 (PIN 4). Its \r\nInterrupt Enable In pin can be tied to any of the other INT pins using the \r\nIEI Select jumper (J4). Selecting the first position of that jumper (INT0) \r\nsets the on-board SIO/2 as the Master. On slave boards, the Interrupt Enable \r\nIn will have 6 positions. Also, a 4 positions IEO jumper header should be \r\nprovided to select the right User Port A IEO position (pins 5-8). More on \r\nthat on the slave board design document.\r\n\r\n**WARNING** User Port A pins 4-8 (interrupts) are not protected. If you \r\nconnect a daughter board without checking jumper settings first, you could \r\nshort an IO pin on your stack and damage a chip! Looking into a solution to \r\nthat in a future revision.\r\n \r\n\r\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fformix%2Fretroz","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fformix%2Fretroz","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fformix%2Fretroz/lists"}